Whistle from my coolant cap. I have the motor craft cap and it whistles and sprays coolant out of it when it is low. I put a gallon in last night drove home 40 miles everything fine. Get up this morning drove 40 miles on the highway and it starts whistling. Get to my job and open the hood. Coolant about a half inch below minimum line. Truck runs fine other then that. I just replaced the fan clutch and the water pump a month ago. Please help

 

Are you the original owner?? Are there studs installed?? Could be a bad cap, cracked degas bottle, or blown head gaskets. So easy steps first to determine the root cause. A pressure test of the degas bottle is one thing to do.

 

Not original owner. the cap is brand new from ford. How do I check head studs? And pressure on the bottle?

 

I am having similar issue. Truck is at shop now oil was leaking from oil Cooler and coolant was bubbling I was down 4L. Removed EGR cooler and coolant still bubbled and boiled. Should I test cap and bottle before jumping right to head gaskets? It has a live wire tuner and was running performance 80hp i think just recently turned it down to towing 60hp and I use it for work and tow about 5000lbs daily.